Adds withdraw functionality

[kelsos]

Repurposes the deposit dialog to act also like a withdraw dialog.

Closes #94

[codecov]

Codecov Report

Merging #98 into master will increase coverage by 0.55%.
The diff coverage is 88.88%.

@@            Coverage Diff             @@
##           master      #98      +/-   ##
==========================================
+ Coverage   79.01%   79.57%   +0.55%     
==========================================
  Files          69       70       +1     
  Lines        1811     1826      +15     
  Branches      196      198       +2     
==========================================
+ Hits         1431     1453      +22     
+ Misses        340      332       -8     
- Partials       40       41       +1

Impacted Files	Coverage Δ
...thdraw-dialog/deposit-withdraw-dialog.component.ts	77.77% <100%> (ø)
...nents/channel-actions/channel-actions.component.ts	100% <100%> (ø)	⬆️
src/app/services/raiden.service.ts	50.93% <100%> (+5.7%)	⬆️
src/app/utils/helpers.ts	100% <100%> (ø)
src/testing/test-data.ts	100% <100%> (ø)	⬆️
...omponents/channel-table/channel-table.component.ts	53.22% <25%> (ø)	⬆️

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[andrevmatos]

lgtm!